[artifactory] Expose podManagementPolicy and update PDB logic for HA deployments

[joshuaauger]

PR Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• Chart Version bumped
• CHANGELOG.md updated
• Variables and other changes are documented in the README.md
• Title of the PR starts with chart name (e.g. [artifactory])

What this PR does / why we need it:

Exposes artifactory.podManagementPolicy in values.yaml (default: OrderedReady) so users
can set it to Parallel to allow independent pod scaling and faster rolling restarts in HA deployments.

Also updates the PDB logic in artifactory-pdb.yaml — a PDB is now created when any of
podManagementPolicy: Parallel, artifactory.minAvailable, or artifactory.maxUnavailable is set.
When Parallel is used or maxUnavailable is explicitly provided, the PDB uses maxUnavailable
(defaulting to 1); otherwise it falls back to minAvailable. This ensures the PDB spec never
has both fields set simultaneously, which is a Kubernetes constraint.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format,
will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

• podManagementPolicy is an immutable field on a StatefulSet. Changing it on an existing
  deployment requires deleting the StatefulSet with --cascade=orphan before upgrading.
  This is called out in the README.
• The PDB maxUnavailable/minAvailable switching logic ensures only one of the two mutually
  exclusive fields is ever rendered in the PDB spec.